In the industry of wellbore drilling it is common practice to drill one or more branch boreholes from a main borehole in order to reach different zones of hydrocarbon containing formations from a single surface location. Such branch boreholes deviate from the main borehole at rather low curvatures due to operational restrictions imposed on the drill strings used. In case the branch borehole is to be drilled into a relatively thin hydrocarbon fluid containing layer, it is difficult or impossible to start drilling of the branch borehole from the main borehole at a location positioned in the layer and to proceed drilling into the layer.